chem question

[kaliluv06]

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I am doing some extra problems to get me ready for my test. I am having issues with this one here. Can someone give me a little hint?

One source of power for heart pacemakers is to implant a zinc electrode and a platinum electrode in body tissue. This cell then draws upon material in the oxygen containing body fluids to complete a reaction where Zn is oxidized and dissolved oxygen is reduced. The pH of blood is about 7.4.

a. Write the half reactions and overall cell reaction for this system.

b. Estimate the potential of the cell. Why is your number an estimate?

c. Suppose that the pacemaker draws a current of 40 microamps. How often does that patient need to have the Zn electrode replaced if those electrodes have a mass of 5.00g?

 

[gschl1234]

Originally posted by kaliluv06
I am doing some extra problems to get me ready for my test. I am having issues with this one here. Can someone give me a little hint?

One source of power for heart pacemakers is to implant a zinc electrode and a platinum electrode in body tissue. This cell then draws upon material in the oxygen containing body fluids to complete a reaction where Zn is oxidized and dissolved oxygen is reduced. The pH of blood is about 7.4.

a. Write the half reactions and overall cell reaction for this system.

b. Estimate the potential of the cell. Why is your number an estimate?

c. Suppose that the pacemaker draws a current of 40 microamps. How often does that patient need to have the Zn electrode replaced if those electrodes have a mass of 5.00g?

What class is this? Do you have the answers in the back of the book or something? I'm not sure whether my solutions are correct. Please let me know.

a. Zn --> Zn2+ + 2e
O2 + 2e --> 2H2O
Balanced Equation:
Zn + O2 + 4H+ --> Zn2+ + 2H2O

b. E1/2 Ox = .762; E1/2 Red = 1.229
Just add the two. The reason this is just an estimate is because the E1/2 I used are derived from comparison with the standard hydrogen electrode. The standard state (chemical standard state, not biochemical) is pH 0, temp either 273 or 298 K (can't remember now) and physiological pH and temp are significantly different thus, you would expecct the actual voltage to be different from the calculated.

c. Not sure how to relate current with mass. Did you have some kind of equation for this?

 

[coldchemist]

She's going to have to relate grams of zinc to moles of zinc to moles of electrons.